Fixed for the PRB allocation issue assert in DLSCH scheduler

The following ASSERT is tirggered while testing 16 UE setup.

Assertion (NPRB>0 && (NPRB + RBstart <= BWPsize)) failed!
In PRBalloc_to_locationandbandwidth0() /home/ran/common/utils/nr/nr_common.c:286
Illegal NPRB/RBstart Configuration (1,48) for BWPsize 48

Corrected the get_start_stop_allocation calculation to fix the issue. The implementation was wrong. The rbstop shall be the last rb that could be allocated. Also the following two conditions are taken care

rbStart needs to be strictly smaller than rbStop

rbStart+rbSize needs to be smaller or equal to rbStop

The problem was that we confounded both conditions, so rbStart could be equal to rbStop, which then leads to one PRB being allocated at the end. Setting rbStop to BWPsize - 1 and making sure the above two conditions are true does not make it lead to wrong allocations anymor